The priest I asked is from the FSSP. His sermons and talks do not betray any sympathy to either Protestantism or the Novus Ordo; as I am not a sedevacantist, I trust him as a source of traditional unadulterated Catholic doctrine - that however, is besides the point. I hesitate to mention his name in such a public forum.
s2srea,
I appreciate your posts. However, I'm still not convinced that playing the organ in and of itself constitutes "participation". You mentioned being a part of a band in the past? Perhaps you know then, how detached a musician can be when practicing his art. It isn't a wonder that so many Protestants and atheists are organists at Catholic churches and never convert - they perform their jobs with the utmost perfection, but yet simultaneously with almost mechanical detachment. Many musicians can retreat into something like a state of interior contemplation when playing music.
As far as I am concerned (and as far as my employer and the congregation is concerned), I am just playing what is put in front of me. Sometimes I pay attention to the lyrics when it is a Catholic hymn or at least a hymn not inimical to the Faith. I sing along when practicing, but never at the actual service.
That said, I know that the above paragraph doesn't really defend my position.
This priest said that what I am doing is not sinful, but since he noted my continual obsessing torment over this question, he told me that if I have qualms about it, I should not do it if I feel like I am sinning - despite the fact that it is not intrinsically sinful.